Spiraled magnetic field synchro



c. E. KEENE 84,632

SPIRALED MAGNETIC FIELD SYNCHRO Filed April 29, 1957 2 Sheets-Sheet 1INVENTOR.

(79ft E. E//' Aug 1, c. E. KEENE SPIRALED MAGNETIC FIELD SYNCHRO FiledApril 29, 1957 2 Sheets-Sheet 2 F 9-- Q INVENT gg United States PatentSPIRALED MAGNETIC FIELD SYNCHRO Carl E. Keene, Lancaster, Calif. I

Application April 29, 1957, Serial No. 655,923

9 Claims. (Cl. 310-27) (Granted under Tifle 35, U. S. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the United States Government for governmental purposes withoutpayment to me of any royalty thereon.

This invention relates to synchros, or self-synchronous electricaldevices, for transmitting motion or positional data. It is the principalobject of the invention to provide a synchro capable of transmittinglinear motion or positional information directly, without resort togears, cams or other mechanical devices for converting rotary motioninto linear motion. A further object of the invention is to provide asynchro capable of converting rotary motion to linear motion, linearmotion to rotary motion and rotary motion to rotary motion in anydesired angular ratio, and in which the motion conversions can be madenon-proportional if desired. The described synchro is electricallysimilar to and can be used in conjunction with synchros of conventionaltype used to transmit angular information.

Briefly the synchro consists of an outer three-winding core surroundingand coaxial with an inner core having two salient poles and a singlewinding as in a conventional synchro. The described synchro differs fromthe conventional synchro, however, in that the inner core is axiallyelongated and the two faces of the salient poles follow helical pathsabout the axes of the core. Therefore, when the inner core is movedaxially relative to the outer core the two salient poles, in effect,rotate within the outer core having an effect electrically similar tothe rotation of the inner core in a conventional synchro. Therefore, iftwo of the described synchros are connected together and energized inthe manner of conventional synchros, the inner cores will assume similaraxial positions relative to their outer cores and any relative axialmotion between the inner and outer cores of one synchro will producesimilar relative axial motion in the other synchro. On the other hand,if relative axial movement of the cores is prevented in the twosynchros, relative rotation of the cores of one synchro will producesimilar relative rotation in the other synchro the same as withconventional synchros. It is evident, therefore, that by the propercombination of permitting and preventing relative axial and rotationalmovement of the cores, linear motion may be converted to angular motionand vice versa.

A more detailed description of this invention will be given inconnection with the specific embodiments thereof shown in theaccompanying drawing, in which Fig. 1 shows a conventional synchrocircuit,

Figs. 2 and 3 illustrate structural details of a conventional synchro, I

Figs. 4 and 5 illustrate the construction of the inner core of a synchroin accordance with the invention,

Fig. 6 shows a synchro circuit employing synchros constructed inaccordance with the invention,

Fig. 7 illustrates a manner of supporting the moving outer core of thesynchro,

2,848,632 Patented Aug. 19, 1958 Fig. 8 illustrates an arrangement fortransmitting or receiving angular motion in a ratio other than unity,and

Fig. 9 shows a core in which the pitch of the pole face helices variesalong the axis.

Referring to the schematic diagram of a conventional synchro systemshown in Fig. l, the shaft 1 of transmitting synchro T is firmly drivenand constitutes the input to the system. The shaft 2 of the receivingsynchro R is caused to follow the angular movements of shaft 1 andconstitutes the output of the system. The transmitting and receivingsynchros are electrically and mechanically similar, except that thereceiving synchro is usually equipped with a damping device and may havebearings of lower friction than are required in the transmitter. Thegeneral physical form of a conventional synchro is illustrated in Figs.2 and 3. The essential elements are an outer cylindrical magnetic coreassembly or stator 3 and an inner magnetic core assembly or rotor 4mounted on shaft S which is concentric with the outer core assembly. Thestator 3 is normally mounted in a housing which supports shaft S insuitable bearings, neither shown in the drawing. The stator 3 consistsof a laminated slotted core carrying the three equal windings 5, 6 and 7(Fig. 1) spaced apart. The windings may be Y-connected, as in Fig. 1, ordelta-connected, the stator being in all respects similar to the statorof a 3-phase motor or generator. The rotor consists of a laminated core8 having two salient poles, the faces of which are designated 9 and 10.The core is wound with a single winding 11 to which connection is madeby slip rings and brushes generally indicated at 12.

Returning to Fig. 1, when the rotor windings 11 are energized withalternating current, voltages are induced in the stator windings bytransformer action. The amplitudes and phases of these alternatingvoltages depend upon the position of the rotor winding relative to thestator, however, the phase of the voltage in any winding will always bethe same as or opposite to that of the power source voltage applied tothe rotor windings. If the rotor windings 11 are energized in parallel,as shown, and shaft 1 is firmly held, the rotor of synchro R will rotateto the position at which the voltages induced in the stator windings ofsynchro R are of the same amplitude and phase as the voltages induced inthe corresponding stator windings of synchro T. When this conditionexists, the currents in connecting lines 12, 13 and 14 are zero and thesystem is in a state of equilibrium. If an angular motion is imparted toshaft 1 changing the position of the rotor Winding 11 of synchro T,rotor winding 11 of synchro R is forced through an equal angulardisplacement to restore the condition of equilibrium. Therefore shaft 2is made to follow the angular movements of shaft 1.

The construction of a synchro in accordance with the invention is shownin Fig. 4. The outer magnetic core assembly 3 is identical to that ofthe conventional synchro described above, connections to the threewindings being made at terminals 15, 16 and 17. The inner magnetic coreassembly 4' is similar electrically to the conventional synchro rotorbut differs structurally. It is similar in that the core has two salientpoles and a single winding. It is different in that the core isconsiderably longer axially than the outer core assembly and in that thetwo salient pole faces follow diametrically opposide helical paths inthe direction of the axis. The helical pole faces are designated 18 and19 in Fig. 4. The core assembly may be constructed by placing a numberof laminations shaped, for example, as shown in the sectional view ofFig. 5, over shaft 20 each being rotated slightly with respect to thepreceding laminations. A key in each lamination may cooperate with aspiral slot 21 o: in the shaft to angularly position the laminations, asshown in Fig. 5, the shaft being slightly larger inside the laminations.The single winding 11' is placed in the two diametrically oppositespiral slots 22 and 23 that result from the shape of the laminationsandtheir angular displacement.

If the outer and inner core assemblies of Fig. 4 are mounted so as topermit relative axial movement but not relative rotation, the relativeaxial movement has the same electrical elfect as rotation of the rotorin a conventional synchro. In other words if coil 11' in Fig. 4 isenergized with alternating current and the terminals 15, 16 and 17 ofouter core assembly 3 are connected to the corresponding terminals of asecond identical outer core assembly, the direction of the resultantmagnetic flux in the second assembly will rotate in response to theaxial movement of inner core assembly 4 relative to its associated outercore assembly 3. The axial length of the core of the inner core assembly4, the pitch of the pole face helices and the axial length of the coreof outer core assembly 3 are normally correlated so that axial movementof assembly 4 relative to assembly 3 from one limit to the other resultsin 360 of rotation of the flux deviation in the second outer coreassembly. 7

The construction of Fig. 4 has the further characteristic that, withrelative axial movement prevented, relative rotation of the outer andinner core assemblies 3 and 4 produces the same voltages at terminals15, 16 and 17 as would be produced at the corresponding terminals of aconventional synchro by turning its rotor. Therefore a synchro of thetype shown in Fig. 4 may be used in conjunction with another similarsynchro for linear-tolinear, linear-to-rotary, rotary-to-linear androtary-torotary motion transmission depending upon the types of relativemotion permitted between the outer and inner core assemblies. These usesare illustrated in Fig. 6.

In Fig. 6, synchro T may be considered the transmitter and synchro R thereceiver. Both synchros are illustrated as being alike, although in apractical embodiment the receiver may differ mechanically from thetransmitter, as in conventional synchros, in having means to reducefriction and provide damping. Disregarding these possible differences,each synchro is constructed in accordance with Fig. 4. The innermagnetic core assembly 4 is journaled in the housing 24 and the outermagnetic core assembly 3 is supported within the housing in a manner topermit axial movement relative to inner element 4 as by rods 25 and 26,shown in Fig. 7. A rod 27 extends through the housing for coupling coreassembly 3 to an external mechanism. Clamps 28 and 29 are provided forlocking core assemblies 4 and 3 against rotation and axial movement,respectively, if desired.

For linear-to-linear motion transmission, clamps 28 in each synchro areengaged to prevent rotation of the inner core assemblies 4 and clamps 29are released to permit axial movement of the outer core assemblies 3.With rod 27 of T firmly held by external means and the windings of theinner core assemblies 4 energized by the application of alternatingvoltage to terminals 31--32, the core assembly 3 of R will assume theposition axially of inner core assembly 4 at which the direction of theresultant flux relative to the three windings of outer assembly 3 is thesame as in T and at which the phase of the flux is the same as in T. Ifthe core assemblies 4 of T and R were initially clamped in the sameangular positions, the above conditions exist when the outer coreassembly 3 of R has the same axial position relative to inner coreassembly 4 that core assembly 3 of T has relative to its associated coreassembly 4'. For linear motion transmission, therefore, rod 27 of T isthe input to the system and any axial movement of this rod in thedirection of the arrows is followed by a corresponding movement of therod 27 of R. The ratio in which the linear motion is transmitted isdetermined by the relative pitches of the helical pole faces in the twosynchros.

If the pitch is the same in the receiver as in the transmitter thetransmission ratio is unity, if the receiver pitch is less than that ofthe transmitter the ratio is less than unity and if the receiver pitchis greater than that of the transmitter the ratio is greater than unity.Nonproportional transmission of linear motion is also possible. This isaccomplished by having the pitch of the helical pole faces in either thetransmitter or receiver, or both, vary along the axis in a desiredmanner. Fig. 7 shows the inner core assembly 4 designed so that thepitch decreases from left to right along the axis.

In linear-to-rotary motion transmission clamp 28 of T and clamp 29 of Rare engaged while clamp 29 of T and clamp 28 of R are disengaged. Withrod 27 of T as the input, movement of this rod in the direction of thearrows causes rotation of inner core assembly 4 and shaft 20 of R. Againthe ratio of motion transmission is determined by the pitch of thehelical pole faces of core assembly 4 in T. Also, the motiontransmission may be made nonproportional by having the pitch of thehelical pole faces in core assembly 4' of T vary along the axis.

Rotary-to-linear transmission may be accomplished by engaging clamp 29of T and clamp 28 of R, and disengaging clamp 28 of T and clamp 29 of R.Rotation of shaft 20 of T in this case causes axial movement of outercore assembly 3 and rod 27 of R. The transmission ratio, as before, canbe controlled by controlling the pitch of the helical pole faces in theinner core assembly 4 of R. Also, as before, the motion transfer may bemade nonproportional by having the pitch of the helices of 4 in R varyalong the axis.

It is also possible to have both rotary and linear inputs to T. In thiscase, one or the other of clamps 28 and 29 of R is engaged dependingupon whether rotary or linear output is desired. The output of R, eitherlinear or rotary, is the sum of two components, one derived from therotary input to T and the other derived from the linear input to T.

With clamps 29 engaged and clamps 28 disengaged in both T and R,rotary-to-rotary motion can be accomplished in the same manner as in aconventional synchro system. With shaft 20 of T as the input of thesystem, any angular displacement of this shaft is accompanied by anequal angular displacement of shaft 20 of R. Therefore, with axialmotion of outer core assembly 3 prevented by clamp 29 and with clamp 28released permitting rotation of shaft 20, the synchro is the electricaland functional equivalent of a conventional synchro and whenever so usedin the preceding examples may be replaced by a conventional synchro.Operation of synchros of the type shown in Fig. 6 in the same systemwith conventional synchros is therefore entirely feasible.

It is sometimes desirable to transmit angular motion in a ratiodifferent from unity. This may be accomplished by the embodiment of Fig.8. In this device the inner magnetic core assembly 4" is rigidlyattached to the housing or body member 33 and is similar in all respectsto core assembly 4 of Fig. 4 except that it may be curved in an arccentered on shaft 34 in order to permit a minimum air gap to the outercore assembly 3 which is carried by arm 35 attached to shaft 34.Assuming R in Fig. 6 to be replaced by the device of Fig. 8, clamp 29 ofT to be engaged and clamp 28 of T to be disengaged, rotation of shaft 20of T through 360 will cause shaft 34 to rotate through the angle A.Therefore, rotation of input shaft 20 through a given angle from itszero position causes shaft 34 to rotate through an angle B equal toA/360 times the given input angle, the transmission ratio A/ 360 in thiscase being less than unity. For a transmission ratio greater than unity,the device of Fig. 8 may be made the transmitter, replacing T in Fig. 6,clamp 29 being engaged and clamp 28 being disengaged in R. In this caserotation of input shaft 34 through an angle B causes shaft 20 of R torotate through an angle equal to 360/11 times B, the transmission ratio360/A now being greater than unity. The magnitude of the transmissionratio depends upon the length of arm 35 and the pitch of the helicalpole faces of core assembly 4". Also, the transmission may be madenonproportional by having the pitch of the pole faces of 4" vary alongthe core axis as in preceding examples.

The device of Fig. 8 may also be used with synchros of the type shown inFig. 6 used as linear transmitters and receivers, i. e., with clamp 29engaged and clamp 28 disengaged, for linear-to-rotary androtary-to-linear transmission. The effect of pole face helix pitch ontransmission ratio and the effect of a variation in pitch along the coreaxis in producing nonproportional transmission are the same in theseapplications as in the preceding examples.

. I claim:

1. A synchro having coaxial outer and inner magnetic core assemblies inwhich the transversely magnetized core of the inner core assembly hastwo salient poles, the faces of which are in the form of diametricallyopposite helices of greater axial extent than the magnetic core of saidouter assembly, and the inner surface of said outer magnetic coreassembly is substantially cylindrical.

2. A synchro having coaxial outer and inner magnetic core assemblies inwhich the transversely magnetized core of the inner core assembly hastwo salient poles, the faces of which are in the form of diametricallyopposite helices of greater axial extent than the magnetic core of saidouter assembly, the inner surface of said outer magnetic assembly beingsubstantially cylindrical, and means providing for relative axialmovement of said core assemblies.

3. A synchro having coaxial outer and inner magnetic core assemblies inwhich the transversely magnetized core of the inner core assembly hastwo salient poles, the faces of which are in the form of diametricallyopposite helices of greater axial extent than the magnetic core of saidouter assembly, the inner surface of said outer magnetic core assemblybeing substantially cylindrical, and means providing for both relativeaxial movement and relative rotational movement of said core assemblies.

4. A synchro having coaxial outer and inner magnetic core assemblies inwhich the magnetic core of the inner core assembly has two salientpoles, the faces of which are in the form of diametrically oppositehelices of greater axial extent than the magnetic core of said outerassembly, and means restricting relative movement of said coreassemblies to relative axial movement.

5. A synchro having coaxial outer and inner magnetic 19 core assembliesin which the magnetic core of the inner core assembly has two salientpoles, the faces of which are in the form of diametrically oppositehelices of greater axial extent than the magnetic core of said outerassembly, means providing for both relative axial movement and relativerotational movement of said core assemblies, and independentlyactuatable means for locking said core assemblies against either of saidrelative movements.

6. A synchro having coaxial outer and inner magnetic core assemblies inwhich the magnetic core of the inner core assembly has two salientpoles, the faces of which are in the form of diametrically oppositehelices of greater axial extent than the magnetic core of said outerassembly, the pitches of said helices varying equally along said innercore assembly.

7. A synchro having coaxial outer and inner magnetic core assemblies inwhich the magnetic core of the inner core assembly has two salientpoles, the faces of which are in the form of diametrically oppositehelices of greater axial extent than the magnetic core of said outerassembly, a'shaft, a body member fixedly supporting said inner coreassembly and rotatably supporting said shaft so that the axis of saidcore assemblies lies in a plane normal to said shaft, and an arm havingone end attached to said shaft and the other end attached to said outercore assembly.

8. Apparatus as claimed in claim 7 in which said inner core assembly hasan arcuate shape of which said shaft is the center.

9. A synchro having an outer magnetic core assembly comprising amagnetic core having a cylindrical opening therein and having threewindings with their centers equally spaced about said opening; an innermagnetic core assembly situated within said opening and concentrictherewith, comprising a magnetic core of greater length than the core ofsaid outer core assembly having two salient poles and a single winding,the faces of said poles being in the form of diametrically oppositehelices; and means providing for relative axial moveemnt of said coreassemblies.

References Cited in the file of this patent UNITED STATES PATENTSLecoche July 2, 1912 Keller et a1. Nov. 5, 1912

